JP2017103214A - Anionic scavenger materials in anode/cathode loop of fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system that includes a component for removing anionic contaminants.SOLUTION: The fuel system includes a fuel cell stack, a fuel gas feed subsystem in communication with fuel cell anodes in the fuel cell stack, an oxygen-containing gas feed subsystem in communication with fuel cell cathodes in the fuel cell stack, and an anionic scavenging subsystem in communication with the fuel gas feed subsystem and/or the oxygen-containing gas feed subsystem.SELECTED DRAWING: Figure 4

Description

Cross-reference of related applications
[0001] This application claims the benefit of US Provisional Application No. 62 / 246,254, filed Oct. 26, 2015, the disclosure of which is hereby incorporated by reference in its entirety.

  [0002] In at least one embodiment, the present invention relates to a method and system for recovery voltage loss in a fuel cell due to anionic contamination.

  [0003] Fuel cells are used as a power source in many applications. In particular, fuel cells are proposed for use in automobiles instead of internal combustion engines. Commonly used fuel cell designs use solid polymer electrolyte (“SPE”) or proton exchange membranes (“PEM”) to provide ion transport between the anode and cathode.

[0004] In proton exchange membrane fuel cells, hydrogen is supplied as fuel to the anode and oxygen is supplied as oxidant to the cathode. The oxygen can be either in pure form (O ₂ ) or air (mixture of O ₂ and N ₂ ). PEM fuel cells typically have a membrane electrode assembly (“MEA”) in which a solid polymer membrane has an anode catalyst on one side and a cathode catalyst on the opposite side. The anode and cathode layers of a typical PEM fuel cell are formed of a porous conductive material such as graphite woven fabric, graphitized sheet or carbon paper, with the fuel and oxidant facing the fuel and oxidant supply electrodes, respectively. Allows dispersion over the surface of the membrane. Each electrode has fine catalyst particles (eg, platinum particles) carried on carbon particles to promote hydrogen oxidation at the anode and oxygen reduction at the cathode. Protons flow from the anode through the ion conducting polymer membrane to the cathode where they combine with oxygen to form water and are discharged from the cell. The MEA is sandwiched between a pair of porous gas diffusion layers (“GDL”), which are then sandwiched between a pair of non-porous conductive elements or plates. The plates serve as current collectors for the anode and cathode and have appropriate flow paths and openings formed therein for distributing the fuel cell gaseous reactants over the surfaces of the respective anode and cathode catalysts. Including. In order to efficiently generate electricity, the polymer electrolyte membrane of a PEM fuel cell must be thin, chemically stable, proton permeable, non-conductive, and gas impermeable. In typical applications, fuel cells are provided in an array of many individual fuel cell stacks to provide a high level of power.

[0005] Although prior art fuel cell systems function fairly well, it is known that chemical degradation of perfluorosulfonic acid (PFSA) type PEM membranes can result in the release of sulfate. In addition, there is a possibility that the SO ₂ from the air is dissolved in water, and is changed to sulfite and sulfate. Sulfates that showed a strong correlation to cell voltage loss are released into the product water during the recovery cycle. Those sulfates will be bound to the anion exchange material in the anode / cathode loop and will therefore not be recycled back to the cell causing a rapid voltage loss. Currently, the recovery procedure during operation is the only effective way to solve the problem of loss of reversible degradation. However, sulfates and other anions that cause electrode contamination may not be completely removed from the system during the recovery cycle.

  [0006] Thus, there is a need for improved methods and systems for preventing fuel cell voltage loss from anionic contaminants.

  [0007] The present invention, in at least one embodiment, solves one or more problems of the prior art by providing a fuel cell system that includes a component for removing anionic contaminants. A fuel cell system includes: a fuel cell stack; a fuel gas supply subsystem in communication with a fuel cell anode in the fuel cell stack; an oxygen-containing gas supply subsystem in communication with a fuel cell cathode in the fuel cell stack; An anion capture subsystem in communication with the gas supply subsystem and / or the oxygen-containing gas supply subsystem. The fuel gas supply subsystem provides fuel to the fuel cell anode, while the oxygen-containing gas supply subsystem provides oxygen-containing gas to the fuel cell anode. The fuel cells in the fuel cell stack release sulfate through membrane degradation, which can be released to the anode / cathode loop and can be recycled back to the cell, thereby causing further voltage loss. is there. Advantageously, the anion capture subsystem removes sulfate and other contaminants (eg, chloride) from the anode or cathode recirculation loop.

  [0008] In another embodiment, a fuel cell system for removing anionic contaminants is provided. A fuel cell system includes: a fuel cell stack; a fuel gas supply subsystem in communication with a fuel cell anode in the fuel cell stack; an oxygen-containing gas supply subsystem in communication with a fuel cell cathode in the fuel cell stack; A first anion capture subsystem in fluid communication with the gas supply subsystem and a second anion capture subsystem in fluid communication with the oxygen-containing gas supply subsystem. The fuel gas supply subsystem provides fuel to the fuel cell anode. The fuel gas supply subsystem also includes an anode loop in which the fuel gas is recirculated and integrated with new fuel at the fuel recombination station. Similarly, the oxygen-containing gas supply subsystem provides oxygen-containing gas to the fuel cell cathode. The oxygen-containing gas supply subsystem also includes a cathode loop in which water is transferred from the outlet to a retractable dry cathode oxygen-containing supply gas by a humidifier. A first anion capture subsystem is positioned between the anode exhaust and the fuel recombination station, while a second anion capture subsystem is positioned between the cathode exhaust and the fuel recombination station.

[0009] FIG. 2 is a schematic cross section of a fuel cell incorporating a carbon-supported catalyst into an anode and / or cathode catalyst layer. [0010] FIG. 5 is a plot illustrating the correlation between recoverable voltage loss and sulfate concentration in fuel cell cathode discharge water. [0011] Provides a plot of the correlation between cell voltage loss and BOP material leaching index. [0012] A schematic diagram of a fuel cell system for removing anionic contaminants is provided.

  [0013] Reference will now be made in detail to the presently preferred configurations, embodiments and methods of the invention, which constitute the best mode of carrying out the invention that the inventors are presently aware of. The figure is not necessarily a fixed ratio. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Accordingly, the specific details disclosed herein are not intended to be limiting, but merely to serve as a representative basis for any aspect of the present invention and / or various uses of the present invention to those skilled in the art. Should be construed as a representative basis for teaching.

  [0014] In the examples or unless otherwise stated, all quantities in this description that indicate physical quantities or conditions of reaction and / or use are intended to describe the word "about" in describing the broadest scope of the invention. Should be understood to be modified by Implementation within the numerical limits specified is generally preferred. Also, unless expressly stated otherwise, percentages, “parts” and ratio values are by weight, and a description of a group or type of material that is appropriate or suitable for a given purpose in connection with the present invention is Meaning that mixing of any two or more of a group or type of members is equally suitable or suitable, and the description of a component in chemical terms is an addition to any compound specified in that description. It refers to the components at the time and does not necessarily exclude chemical interactions between the components of the mixture once mixed, the initial definition of an acronym or other abbreviation is the same abbreviation of this specification Applies to all subsequent uses in the document and applies mutatis mutandis to the usual grammatical changes of the abbreviations defined at the beginning, and unless otherwise stated, the measure of a property is the Or determined by the same technique as mentioned later in front.

  [0015] It should also be understood that the invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions may of course vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the invention and is not intended to be limiting in any way.

  [0016] The term “comprising” is synonymous with “comprising”, “having”, “containing” or “characterizing”. These terms are comprehensive and open-ended and do not exclude additional, non-enumerated elements or method steps.

  [0017] The phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a main section rather than immediately after the preamble of a claim, it limits only those elements described in that section and does not exclude other elements from the entire claim.

  [0018] The phrase “consisting essentially of” limits the scope of the claim to the material or steps specified, as well as to those that do not substantially affect the basic and novel characteristics of the claimed subject matter. To do.

  [0019] With respect to the terms "comprising", "consisting of", and "consisting essentially of" when one of these three terms is used herein, the present disclosure and claims The subject matter covered can include the use of either of the other two terms.

  [0020] It should also be noted that as used in this specification and the appended claims, the singular forms “a” and “the” include plural referents unless the context clearly indicates otherwise. I must. For example, reference to a part in the singular is intended to include a plurality of parts.

[0021] Abbreviations
[0022] "RT" means room temperature.
[0023] When publications are referenced throughout this application, the disclosures of these publications are hereby incorporated herein by reference in their entirety and more fully describe the state of the art to which this invention belongs.

[0024] FIG. 1 provides a cross-sectional view of a fuel cell that can be incorporated into a fuel cell system from which anionic contaminants are removed. The PEM fuel cell 10 includes a polymer ion conductive membrane 12 disposed between a cathode electrocatalyst layer 14 and an anode electrocatalyst layer 16. The fuel cell 10 also includes conductive flow field plates 20, 22 that include gas flow paths 24 and 26. The flow field plates 20, 22 are bipolar plates (illustrated) or monopolar plates (ie, end plates). In an improvement, the flow field plates 20, 22 are formed from a metal plate (eg, stainless steel) that is optionally coated with a noble metal such as gold or platinum. In another refinement, the flow field plates 20, 22 are formed from a conductive polymer that is also optionally coated with a noble metal. Gas diffusion layers 32 and 34 are also interposed between the flow field plate and the catalyst layer. During operation, hydrogen is supplied as fuel to the anode catalyst layer 16 and oxygen is supplied as oxidant to the cathode catalyst layer 14 thereby generating electricity as a result of the electrochemical process therein. However, one complication of fuel cell operation is the degradation of the polymer ion conducting membrane that can release sulfate. In addition, there is a possibility that the SO ₂ from the air is dissolved in water, and is changed to sulfite and sulfate. As an example, Table 1 illustrates the fuel cell voltage (V1) at the first time and the fuel cell voltage (V2) at a later time after exposure to ppb levels of SO _{2 in} air. This table illustrates the effect of SO ₂ from ambient air on a cell operating at 0.2 A / cm ² .

FIG. 2 provides a plot illustrating the correlation between recoverable voltage loss and sulfate concentration in the fuel cell cathode discharge water. Similarly, FIG. 3 provides a plot of the correlation between cell voltage loss and BOP material leaching index. The harmful effects of sulfate on fuel cell performance cannot be clearly denied.

  [0025] Referring to FIG. 4, a schematic diagram of a fuel cell system for removing anionic contaminants is provided. The fuel cell system 40 includes a fuel cell stack 42 that includes one or more individual fuel cells 44. In an improvement, the fuel cell 44 is according to the general design depicted in FIG. 1 and its associated description. In one refinement, the fuel cell stack 42 includes 5 to 400 fuel cells. The fuel cell system 40 also includes a fuel gas supply subsystem 46 in communication with the fuel cell anode in the fuel cell stack 42 and an oxygen-containing gas supply subsystem 48 in communication with the fuel cell cathode in the fuel cell stack 42.

  [0026] Still referring to FIG. 4, the fuel gas supply subsystem 46 includes a fuel source 50 that provides a fuel-containing gas to the fuel cell stack 42, particularly to the fuel cell anode. Typically, the fuel contains molecular hydrogen. The fuel enters the fuel cell stack and contacts the fuel cell anode, particularly the anode catalyst layer of the fuel cell. In some variations, the fuel gas supply subsystem 46 includes an anode loop 52 in which fuel is recirculated from the anode exhaust 53 and integrated with new fuel at the fuel recombination station 54. In this situation, the anode loop 52 includes a total flow path from the recombination station 54 through the fuel cell stack and back to the fuel recombination station 54.

  Still referring to FIG. 4, the oxygen-containing gas supply subsystem 48 includes an oxygen-containing gas source 60 that provides an oxygen-containing gas to the fuel cell stack 42. Typically, the oxygen-containing gas includes molecular oxygen (eg, air). The oxygen-containing gas enters the fuel cell stack and contacts the fuel cell cathode, particularly the cathode catalyst layer of the fuel cell. In some variations, the oxygen-containing gas supply subsystem 48 includes a cathode loop 62 in which water is transferred from the cathode discharge 63 of the fuel cell cathode to a drawn dry cathode oxygen-containing supply gas (eg, air) via a humidifier 64. including. In this situation, the cathode loop 62 includes a full flow path from the humidifier 64 through the fuel cell stack and back to the humidifier 64.

  [0028] Still referring to FIG. 4, the fuel cell system 40 includes an anion capture subsystem 66 and / or 68 in communication with a fuel gas supply subsystem 46 and / or an oxygen-containing gas supply subsystem 48. In some variations, the fuel cell system 40 includes one or both of anion capture subsystems 66 and / or 68. Anion capture subsystems 66 and 68 remove sulfates and optionally other contaminants from the anode or cathode recirculation loop. An anion capture subsystem 66 is positioned in the anode recirculation loop 52 between the anode outlet 53 and the recombination station 54. Similarly, the anion trapping subsystem 68 is positioned in the cathode loop 62 between the cathode outlet 63 and the humidifier 64. The humidifier 64 transfers the water formed in the wet output cathode gas of the fuel cell to the dry entrained oxygen-containing gas to humidify the gas. Thus, the humidifier provides a path for anionic contaminants to pass from the cathode outlet of the fuel cell stack back to the cathode inlet. In an improvement, the anion trapping subsystem 66 is positioned between the cathode outlet and the humidifier 64, thereby reducing the amount of anionic contaminants that pass back to the oxygen-containing gas. In an improvement, the anion capture subsystems 66 and 68 each independently remove at least 80 weight percent of anionic contaminants in the fuel gas and oxygen-containing gas, respectively. In another improvement, anion capture subsystems 66 and 68 each independently remove at least 90 weight percent of anionic contaminants in the fuel gas and oxygen-containing gas, respectively. In yet another improvement, anion capture subsystems 66 and 68 each independently remove 80-100 weight percent of anionic contaminants in the fuel gas and oxygen-containing gas. In yet another improvement, anion capture subsystems 66 and 68 each independently remove 90-98 weight percent of anionic contaminants in the fuel gas and oxygen-containing gas. With respect to these weight percentages, the weight percent is the weight of gas flowing to the capture subsystem.

[0029] In a variation, the anion capture subsystems 66 and 68 include an anion exchange resin or ionomer (common functional group: quaternary ammonium) in the hydroxide (OH ⁻ ) form. It should be appreciated that the resin can be washed to remove any contamination prior to use. Moreover, the resin can be regenerated or replaced during operation.

  [0030] Tables 2 and 3 provide the measured anion removal percentage at equilibrium for the test anion exchange resin that was Amberlyst® A26 in hydroxide form.

It is observed that an anion exchange resin has a high selectivity for sulfate when there is excessive competition for anions in solution. Moreover, no significant difference was observed in the ability to remove anions under different temperature conditions over 3 days.

  [0031] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, it is understood that the terminology used herein is descriptive rather than limiting, and that various changes may be made without departing from the spirit and scope of the invention. In addition, features of various implementations may be combined to form further embodiments of the invention.

DESCRIPTION OF SYMBOLS 10 PEM fuel cell 12 Polymer ion conductive film 14 Cathode electrocatalyst layer 16 Anode electrocatalyst layer 20 Conductive flow field plate 22 Conductive flow field plate 24 Gas flow path 26 Gas flow path 32 Gas diffusion layer 34 Gas diffusion layer 40 Fuel cell system 42 Fuel cell stack 44 Fuel cell 46 Fuel gas supply subsystem 48 Oxygen-containing gas supply subsystem 50 Fuel source 52 Anode loop, anode recirculation loop 53 Anode outlet 54 Fuel recombination station 60 Oxygen-containing gas source 62 Cathode loop 63 Cathode Discharge unit 64 Humidifier 66 Anion capture subsystem 68 Anion capture subsystem

Cross-reference of related applications
[0001] This application claims the benefit of US Provisional Application No. 62 / 246,254, filed Oct. 26, 2015, the disclosure of which is hereby incorporated by reference in its entirety.

  [0002] In at least one embodiment, the present invention relates to a method and system for recovery voltage loss in a fuel cell due to anionic contamination.

  [0003] Fuel cells are used as a power source in many applications. In particular, fuel cells are proposed for use in automobiles instead of internal combustion engines. Commonly used fuel cell designs use solid polymer electrolyte (“SPE”) or proton exchange membranes (“PEM”) to provide ion transport between the anode and cathode.

[0004] In proton exchange membrane fuel cells, hydrogen is supplied as fuel to the anode and oxygen is supplied as oxidant to the cathode. The oxygen can be either in pure form (O ₂ ) or air (mixture of O ₂ and N ₂ ). PEM fuel cells typically have a membrane electrode assembly (“MEA”) in which a solid polymer membrane has an anode catalyst on one side and a cathode catalyst on the opposite side. The anode and cathode layers of a typical PEM fuel cell are formed of a porous conductive material such as graphite woven fabric, graphitized sheet or carbon paper, with the fuel and oxidant facing the fuel and oxidant supply electrodes, respectively. Allows dispersion over the surface of the membrane. Each electrode has fine catalyst particles (eg, platinum particles) carried on carbon particles to promote hydrogen oxidation at the anode and oxygen reduction at the cathode. Protons flow from the anode through the ion conducting polymer membrane to the cathode where they combine with oxygen to form water and are discharged from the cell. The MEA is sandwiched between a pair of porous gas diffusion layers (“GDL”), which are then sandwiched between a pair of non-porous conductive elements or plates. The plates serve as current collectors for the anode and cathode and have appropriate flow paths and openings formed therein for distributing the fuel cell gaseous reactants over the surfaces of the respective anode and cathode catalysts. Including. In order to efficiently generate electricity, the polymer electrolyte membrane of a PEM fuel cell must be thin, chemically stable, proton permeable, non-conductive, and gas impermeable. In typical applications, fuel cells are provided in an array of many individual fuel cell stacks to provide a high level of power.

[0005] Although prior art fuel cell systems function fairly well, it is known that chemical degradation of perfluorosulfonic acid (PFSA) type PEM membranes can result in the release of sulfate. In addition, there is a possibility that the SO ₂ from the air is dissolved in water, and is changed to sulfite and sulfate. Sulfates that showed a strong correlation to cell voltage loss are released into the product water during the recovery cycle. Those sulfates will be bound to the anion exchange material in the anode / cathode loop and will therefore not be recycled back to the cell causing a rapid voltage loss. Currently, the recovery procedure during operation is the only effective way to solve the problem of loss of reversible degradation. However, sulfates and other anions that cause electrode contamination may not be completely removed from the system during the recovery cycle.

  [0006] Thus, there is a need for improved methods and systems for preventing fuel cell voltage loss from anionic contaminants.

[0007] The present invention, in at least one embodiment, solves one or more problems of the prior art by providing a fuel cell system that includes a component for removing anionic contaminants. A fuel cell system includes: a fuel cell stack; a fuel gas supply subsystem in communication with a fuel cell anode in the fuel cell stack; an oxygen-containing gas supply subsystem in communication with a fuel cell cathode in the fuel cell stack; An anion capture subsystem in communication with the gas supply subsystem and / or the oxygen-containing gas supply subsystem. The fuel gas supply subsystem provides fuel to the fuel cell anode, while the oxygen-containing gas supply subsystem provides oxygen-containing gas to the fuel cell cathode . The fuel cells in the fuel cell stack release sulfate through membrane degradation, which can be released to the anode / cathode loop and can be recycled back to the cell, thereby causing further voltage loss. is there. Advantageously, the anion capture subsystem removes sulfate and other contaminants (eg, chloride) from the anode or cathode recirculation loop.

[0008] In another embodiment, a fuel cell system for removing anionic contaminants is provided. A fuel cell system includes: a fuel cell stack; a fuel gas supply subsystem in communication with a fuel cell anode in the fuel cell stack; an oxygen-containing gas supply subsystem in communication with a fuel cell cathode in the fuel cell stack; A first anion capture subsystem in fluid communication with the gas supply subsystem and a second anion capture subsystem in fluid communication with the oxygen-containing gas supply subsystem. The fuel gas supply subsystem provides fuel to the fuel cell anode. The fuel gas supply subsystem also includes an anode loop in which the fuel gas is recirculated and integrated with new fuel at the fuel recombination station. Similarly, the oxygen-containing gas supply subsystem provides oxygen-containing gas to the fuel cell cathode. The oxygen-containing gas supply subsystem also includes a cathode loop in which water is transferred from the outlet to a retractable dry cathode oxygen-containing supply gas by a humidifier. A first anion trapping subsystem is positioned between the anode outlet and the fuel recombination station, while a second anion trapping subsystem is positioned between the cathode outlet and the humidifier .

  In the present specification, at least the following aspects are described.
(Aspect 1)
  A fuel cell system for removing anionic contaminants,
  A fuel cell stack;
  A fuel gas supply subsystem in communication with a fuel cell anode in the fuel cell stack, the fuel gas supply subsystem providing fuel gas to the fuel cell anode;
  An oxygen-containing gas supply subsystem in communication with a fuel cell cathode in the fuel cell stack, the oxygen-containing gas supply subsystem providing an oxygen-containing gas to the fuel cell cathode;
  A fuel cell system comprising: the fuel gas supply subsystem and / or an anion capture subsystem in communication with the oxygen-containing gas supply subsystem.
(Aspect 2)
  The fuel cell system of embodiment 1, wherein the anion trapping subsystem comprises an anion exchange resin or an ionomer.
(Aspect 3)
  The fuel cell system according to aspect 2, wherein the anion exchange resin or ionomer is in a hydroxide form.
(Aspect 4)
  The fuel cell system according to aspect 2, wherein the anion exchange resin or ionomer contains a quaternary ammonium group.
(Aspect 5)
  The fuel cell system of aspect 1, further comprising an anode loop in which the fuel gas is recirculated and integrated with new fuel at a fuel recombination station.
(Aspect 6)
  The fuel cell system according to aspect 5, wherein the anion trapping subsystem is positioned between an anode outlet and the fuel recombination station.
(Aspect 7)
  The fuel cell system according to aspect 1, wherein the oxygen-containing gas supply subsystem includes a cathode loop in which water is transferred from a cathode discharge to a retractable dry cathode oxygen-containing supply gas by a humidifier.
(Aspect 8)
  8. The fuel cell system according to aspect 7, wherein an anion capture subsystem is positioned between the cathode exhaust and the humidifier.
(Aspect 9)
  The fuel cell system according to aspect 1, wherein the fuel gas is molecular hydrogen.
(Aspect 10)
  The fuel cell system according to aspect 1, wherein the oxygen-containing gas is molecular oxygen.
(Aspect 11)
  The fuel cell system according to aspect 1, wherein the anion trapping subsystem removes at least 80 weight percent of the anion contaminant in the fuel gas and / or oxygen-containing gas.
(Aspect 12)
  A fuel cell system for removing anionic contaminants,
  A fuel cell stack;
  A fuel gas supply subsystem in communication with a fuel cell anode in the fuel cell stack, providing fuel gas to the fuel cell anode, wherein the fuel gas supply subsystem is configured to recycle the fuel gas A fuel gas supply subsystem including an anode loop integrated with new fuel at the recombination station;
  An oxygen-containing gas supply subsystem in communication with a fuel cell cathode in the fuel cell stack, the oxygen-containing gas supply subsystem providing an oxygen-containing gas to the fuel cell cathode, wherein the oxygen-containing gas supply subsystem includes water from a cathode discharge section. An oxygen-containing gas supply subsystem that includes a cathode loop that is transferred to a retractable dry cathode oxygen-containing supply gas by a humidifier;
  A first anion capture subsystem positioned between an anode discharge and the fuel recombination station;
  A fuel cell system comprising a second anion capture subsystem positioned between a cathode discharge and the humidifier.
(Aspect 13)
  The fuel cell system according to aspect 12, wherein the first anion capture subsystem and the second anion capture subsystem each independently comprise an anion exchange resin or an ionomer.
(Aspect 14)
  The fuel cell system according to aspect 13, wherein the anion exchange resin or ionomer is in a hydroxide form.
(Aspect 15)
  The fuel cell system according to aspect 13, wherein the anion exchange resin or ionomer contains a quaternary ammonium group.
(Aspect 16)
  The fuel cell system according to aspect 13, wherein the fuel gas is molecular hydrogen.
(Aspect 17)
  The fuel cell system according to aspect 13, wherein the oxygen-containing gas is molecular oxygen.
(Aspect 18)
  In embodiment 13, the first anion scavenging subsystem and the second anion scavenging subsystem each independently remove at least 80 weight percent of the anionic contaminants in the fuel gas and / or oxygen-containing gas. The fuel cell system described.

[0009] FIG. 2 is a schematic cross section of a fuel cell incorporating a carbon-supported catalyst into an anode and / or cathode catalyst layer. [0010] FIG. 5 is a plot illustrating the correlation between recoverable voltage loss and sulfate concentration in fuel cell cathode discharge water. [0011] Provides a plot of the correlation between cell voltage loss and BOP material leaching index. [0012] A schematic diagram of a fuel cell system for removing anionic contaminants is provided.

  [0013] Reference will now be made in detail to the presently preferred configurations, embodiments and methods of the invention, which constitute the best mode of carrying out the invention that the inventors are presently aware of. The figure is not necessarily a fixed ratio. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Accordingly, the specific details disclosed herein are not intended to be limiting, but merely to serve as a representative basis for any aspect of the present invention and / or various uses of the present invention to those skilled in the art. Should be construed as a representative basis for teaching.

  [0014] In the examples or unless otherwise stated, all quantities in this description that indicate physical quantities or conditions of reaction and / or use are intended to describe the word "about" in describing the broadest scope of the invention. Should be understood to be modified by Implementation within the numerical limits specified is generally preferred. Also, unless expressly stated otherwise, percentages, “parts” and ratio values are by weight, and a description of a group or type of material that is appropriate or suitable for a given purpose in connection with the present invention is Meaning that mixing of any two or more of a group or type of members is equally suitable or suitable, and the description of a component in chemical terms is an addition to any compound specified in that description. It refers to the components at the time and does not necessarily exclude chemical interactions between the components of the mixture once mixed, the initial definition of an acronym or other abbreviation is the same abbreviation of this specification Applies to all subsequent uses in the document and applies mutatis mutandis to the usual grammatical changes of the abbreviations defined at the beginning, and unless otherwise stated, the measure of a property is the Or determined by the same technique as mentioned later in front.

  [0015] It should also be understood that the invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions may of course vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the invention and is not intended to be limiting in any way.

  [0016] The term “comprising” is synonymous with “comprising”, “having”, “containing” or “characterizing”. These terms are comprehensive and open-ended and do not exclude additional, non-enumerated elements or method steps.

  [0017] The phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. When this phrase appears in a main section rather than immediately after the preamble of a claim, it limits only those elements described in that section and does not exclude other elements from the entire claim.

  [0018] The phrase “consisting essentially of” limits the scope of the claim to the material or steps specified, as well as to those that do not substantially affect the basic and novel characteristics of the claimed subject matter. To do.

  [0019] With respect to the terms "comprising", "consisting of", and "consisting essentially of" when one of these three terms is used herein, the present disclosure and claims The subject matter covered can include the use of either of the other two terms.

  [0020] It should also be noted that as used in this specification and the appended claims, the singular forms “a” and “the” include plural referents unless the context clearly indicates otherwise. I must. For example, reference to a part in the singular is intended to include a plurality of parts.

[0021] Abbreviations
[0022] "RT" means room temperature.
[0023] When publications are referenced throughout this application, the disclosures of these publications are hereby incorporated herein by reference in their entirety and more fully describe the state of the art to which this invention belongs.

[0024] FIG. 1 provides a cross-sectional view of a fuel cell that can be incorporated into a fuel cell system from which anionic contaminants are removed. The PEM fuel cell 10 includes a polymer ion conductive membrane 12 disposed between a cathode electrocatalyst layer 14 and an anode electrocatalyst layer 16. The fuel cell 10 also includes conductive flow field plates 20, 22 that include gas flow paths 24 and 26. The flow field plates 20, 22 are bipolar plates (illustrated) or monopolar plates (ie, end plates). In an improvement, the flow field plates 20, 22 are formed from a metal plate (eg, stainless steel) that is optionally coated with a noble metal such as gold or platinum. In another refinement, the flow field plates 20, 22 are formed from a conductive polymer that is also optionally coated with a noble metal. Gas diffusion layers 32 and 34 are also interposed between the flow field plate and the catalyst layer. During operation, hydrogen is supplied as fuel to the anode catalyst layer 16 and oxygen is supplied as oxidant to the cathode catalyst layer 14 thereby generating electricity as a result of the electrochemical process therein. However, one complication of fuel cell operation is the degradation of the polymer ion conducting membrane that can release sulfate. In addition, there is a possibility that the SO ₂ from the air is dissolved in water, and is changed to sulfite and sulfate. As an example, Table 1 illustrates the fuel cell voltage (V1) at the first time and the fuel cell voltage (V2) at a later time after exposure to ppb levels of SO _{2 in} air. This table illustrates the effect of SO ₂ from ambient air on a cell operating at 0.2 A / cm ² .

FIG. 2 provides a plot illustrating the correlation between recoverable voltage loss and sulfate concentration in the fuel cell cathode discharge water. Similarly, FIG. 3 provides a plot of the correlation between cell voltage loss and BOP material leaching index. The harmful effects of sulfate on fuel cell performance cannot be clearly denied.

  [0025] Referring to FIG. 4, a schematic diagram of a fuel cell system for removing anionic contaminants is provided. The fuel cell system 40 includes a fuel cell stack 42 that includes one or more individual fuel cells 44. In an improvement, the fuel cell 44 is according to the general design depicted in FIG. 1 and its associated description. In one refinement, the fuel cell stack 42 includes 5 to 400 fuel cells. The fuel cell system 40 also includes a fuel gas supply subsystem 46 in communication with the fuel cell anode in the fuel cell stack 42 and an oxygen-containing gas supply subsystem 48 in communication with the fuel cell cathode in the fuel cell stack 42.

  [0026] Still referring to FIG. 4, the fuel gas supply subsystem 46 includes a fuel source 50 that provides a fuel-containing gas to the fuel cell stack 42, particularly to the fuel cell anode. Typically, the fuel contains molecular hydrogen. The fuel enters the fuel cell stack and contacts the fuel cell anode, particularly the anode catalyst layer of the fuel cell. In some variations, the fuel gas supply subsystem 46 includes an anode loop 52 in which fuel is recirculated from the anode exhaust 53 and integrated with new fuel at the fuel recombination station 54. In this situation, the anode loop 52 includes a total flow path from the recombination station 54 through the fuel cell stack and back to the fuel recombination station 54.

  Still referring to FIG. 4, the oxygen-containing gas supply subsystem 48 includes an oxygen-containing gas source 60 that provides an oxygen-containing gas to the fuel cell stack 42. Typically, the oxygen-containing gas includes molecular oxygen (eg, air). The oxygen-containing gas enters the fuel cell stack and contacts the fuel cell cathode, particularly the cathode catalyst layer of the fuel cell. In some variations, the oxygen-containing gas supply subsystem 48 includes a cathode loop 62 in which water is transferred from the cathode discharge 63 of the fuel cell cathode to a drawn dry cathode oxygen-containing supply gas (eg, air) via a humidifier 64. including. In this situation, the cathode loop 62 includes a full flow path from the humidifier 64 through the fuel cell stack and back to the humidifier 64.

  [0028] Still referring to FIG. 4, the fuel cell system 40 includes an anion capture subsystem 66 and / or 68 in communication with a fuel gas supply subsystem 46 and / or an oxygen-containing gas supply subsystem 48. In some variations, the fuel cell system 40 includes one or both of anion capture subsystems 66 and / or 68. Anion capture subsystems 66 and 68 remove sulfates and optionally other contaminants from the anode or cathode recirculation loop. An anion capture subsystem 66 is positioned in the anode recirculation loop 52 between the anode outlet 53 and the recombination station 54. Similarly, the anion trapping subsystem 68 is positioned in the cathode loop 62 between the cathode outlet 63 and the humidifier 64. The humidifier 64 transfers the water formed in the wet output cathode gas of the fuel cell to the dry entrained oxygen-containing gas to humidify the gas. Thus, the humidifier provides a path for anionic contaminants to pass from the cathode outlet of the fuel cell stack back to the cathode inlet. In an improvement, the anion trapping subsystem 66 is positioned between the cathode outlet and the humidifier 64, thereby reducing the amount of anionic contaminants that pass back to the oxygen-containing gas. In an improvement, the anion capture subsystems 66 and 68 each independently remove at least 80 weight percent of anionic contaminants in the fuel gas and oxygen-containing gas, respectively. In another improvement, anion capture subsystems 66 and 68 each independently remove at least 90 weight percent of anionic contaminants in the fuel gas and oxygen-containing gas, respectively. In yet another improvement, anion capture subsystems 66 and 68 each independently remove 80-100 weight percent of anionic contaminants in the fuel gas and oxygen-containing gas. In yet another improvement, anion capture subsystems 66 and 68 each independently remove 90-98 weight percent of anionic contaminants in the fuel gas and oxygen-containing gas. With respect to these weight percentages, the weight percent is the weight of gas flowing to the capture subsystem.

[0029] In a variation, the anion capture subsystems 66 and 68 include an anion exchange resin or ionomer (common functional group: quaternary ammonium) in the hydroxide (OH ⁻ ) form. It should be appreciated that the resin can be washed to remove any contamination prior to use. Moreover, the resin can be regenerated or replaced during operation.

  [0030] Tables 2 and 3 provide the measured anion removal percentage at equilibrium for the test anion exchange resin that was Amberlyst® A26 in hydroxide form.

It is observed that an anion exchange resin has a high selectivity for sulfate when there is excessive competition for anions in solution. Moreover, no significant difference was observed in the ability to remove anions under different temperature conditions over 3 days.

  [0031] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, it is understood that the terminology used herein is descriptive rather than limiting, and that various changes may be made without departing from the spirit and scope of the invention. In addition, features of various implementations may be combined to form further embodiments of the invention.

DESCRIPTION OF SYMBOLS 10 PEM fuel cell 12 Polymer ion conductive film 14 Cathode electrocatalyst layer 16 Anode electrocatalyst layer 20 Conductive flow field plate 22 Conductive flow field plate 24 Gas flow path 26 Gas flow path 32 Gas diffusion layer 34 Gas diffusion layer 40 Fuel cell system 42 Fuel cell stack 44 Fuel cell 46 Fuel gas supply subsystem 48 Oxygen-containing gas supply subsystem 50 Fuel source 52 Anode loop, anode recirculation loop 53 Anode outlet 54 Fuel recombination station 60 Oxygen-containing gas source 62 Cathode loop 63 Cathode Discharge unit 64 Humidifier 66 Anion capture subsystem 68 Anion capture subsystem

Claims (18)

A fuel cell system for removing anionic contaminants,
A fuel cell stack;
A fuel gas supply subsystem in communication with a fuel cell anode in the fuel cell stack, the fuel gas supply subsystem providing fuel gas to the fuel cell anode;
An oxygen-containing gas supply subsystem in communication with a fuel cell cathode in the fuel cell stack, the oxygen-containing gas supply subsystem providing an oxygen-containing gas to the fuel cell anode;
A fuel cell system comprising: the fuel gas supply subsystem and / or an anion capture subsystem in communication with the oxygen-containing gas supply subsystem.   The fuel cell system of claim 1, wherein the anion trapping subsystem comprises an anion exchange resin or ionomer.   The fuel cell system according to claim 2, wherein the anion exchange resin or ionomer is in a hydroxide form.   The fuel cell system according to claim 2, wherein the anion exchange resin or ionomer contains a quaternary ammonium group.   The fuel cell system of claim 1, further comprising an anode loop in which the fuel gas is recirculated and integrated with new fuel at a fuel recombination station.   The fuel cell system of claim 5, wherein the anion trapping subsystem is positioned between an anode outlet and the fuel recombination station.   The fuel cell system of claim 1, wherein the oxygen-containing gas supply subsystem includes a cathode loop in which water is transferred from a cathode discharge to a retractable dry cathode oxygen-containing supply gas by a humidifier.   The fuel cell system of claim 7, wherein an anion trapping subsystem is positioned between a cathode exhaust and the humidifier.   The fuel cell system according to claim 1, wherein the fuel gas is molecular hydrogen.   The fuel cell system according to claim 1, wherein the oxygen-containing gas is molecular oxygen.   The fuel cell system of claim 1, wherein the anion trapping subsystem removes at least 80 weight percent of the anionic contaminants in the fuel gas and / or oxygen-containing gas. A fuel cell system for removing anionic contaminants,
A fuel cell stack;
A fuel gas supply subsystem in communication with a fuel cell anode in the fuel cell stack, providing fuel gas to the fuel cell anode, wherein the fuel gas supply subsystem is configured to recycle the fuel gas A fuel gas supply subsystem including an anode loop integrated with new fuel at the recombination station;
An oxygen-containing gas supply subsystem in communication with a fuel cell cathode in the fuel cell stack, the oxygen-containing gas supply subsystem providing an oxygen-containing gas to the fuel cell anode, wherein the oxygen-containing gas supply subsystem includes water from a cathode discharge An oxygen-containing gas supply subsystem that includes a cathode loop that is transferred to a retractable dry cathode oxygen-containing supply gas by a humidifier;
A first anion capture subsystem positioned between an anode discharge and the fuel recombination station;
A fuel cell system comprising a second anion capture subsystem positioned between a cathode discharge and the fuel recombination station.   13. The fuel cell system according to claim 12, wherein the first anion capture subsystem and the second anion capture subsystem each independently comprise an anion exchange resin or ionomer.   The fuel cell system of claim 13, wherein the anion exchange resin or ionomer is in hydroxide form.   14. The fuel cell system according to claim 13, wherein the anion exchange resin or ionomer includes a quaternary ammonium group.   The fuel cell system according to claim 13, wherein the fuel gas is molecular hydrogen.   The fuel cell system according to claim 13, wherein the oxygen-containing gas is molecular oxygen.   14. The first anion scavenging subsystem and the second anion scavenging subsystem each independently remove at least 80 weight percent of the anionic contaminants in the fuel gas and / or oxygen-containing gas. The fuel cell system described in 1.

Images